I am a US Citizen filing an I-30 for my spouse.

i am living in Nigeria presently,can a file I-30 for my wife and conclude the process without travelling to the U S A .
which visa superceeds the other, one issued outside U S A or the one giving at U S A entry by U S immigration.?

Yes, you can conclude the process without coming to the U.S....sort of. Your spouse doesn't become a lawful permanent resident until your spouse enters the U.S. and is inspected. Then your spouse becomes a permanent resident of the U.S.

Yes, the process can be completed in Nigeria. But, the US citizen must come to the US at the same time as the alien immigrant.

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